The Mest (mesoderm-specific transcript) gene has been considered an imprinting gene in human and mouse, and was also confirmed in other mammals and flowering plants. To investigate the function and evolution of this gene, the cDNA of full length Mest gene was obtained using 5'- and 3'-RACE from the Chinese Large Toad ( Bufogargarizans). The transcript is 1 325 bp in length which contains a complete open reading frame (ORF) encoding a polypeptide of 326 amino acids (GenBank accession number: ABQ10905). There is a typical α/β hydrolase fold domain in the putative gene product, and it shows high similarity to sequence of homologous protein of Xenopus tropicali (86%), mammlian (70% . 80%). RT-PCR (reverse transcriptase-polymerase chain reaction) analysis demonstrated that the Bufo gargarizans Mest (BgMest) gene is expressed widely in testis, ovary, liver, kidney, spleen, brain, stomach and lung. The conservation of the BgMest gene sequences, protein secondary structure of the BgMest protein, in addition to the expression pattern of the BgMest gene, suggested that the function of BgMest was conserved in amphibians. However, the phylogenetic tree of the imprinting gene of the mammals and other vertebrates examined in this study indicated their divergent origins.